The invention relates to a device for burning a gaseous fuel/oxidant mixture, in particular for a power plant installation.
EP 0 833 105 A2 discloses a premix burner, in which a conical inner body that converges in the flow direction is arranged in an inside chamber. An outer enclosure of the inside chamber is interrupted by tangentially positioned air engagement channels, through which a combustion air flow flows into the inside chamber. As a result, a swirl flow is able to form in the inside chamber, which swirl flow is then enriched by means of at least one fuel nozzle with a fuel. The mixture of both media is then formed in the following mixing pipe. The mixing pipe then changes, via a cross-section increase, into a combustion chamber, whereby a reflux zone that ensures the combustion stability then forms in the region of the plane of the cross-section increase. In order to construct such a mixing pipe, the known premix burner requires a relatively large installation space. In the absence of the mixing pipe, the stability and homogeneity of the flames in the combustion chamber is reduced. There is also a risk of pressure pulsations.
U.S. Pat. Nos. 5,202,303 and 5,328,359 disclose catalyzers constructed from corrugated or folded web material, whereby their folds or corrugations form a plurality of flow channels. A fuel/oxidant mixture is partially burned when flowing through such a catalyzer. In order to prevent overheating in such a catalyzer, the combustion must be limited to only part of the mixture flowing through the catalyzer. For this purpose, only some of the channels are constructed catalytically active, for example by way of an appropriate coating, while the other channels are catalytically inactive. When flowing through the catalyzer, combustion then takes place only inside the catalytically active channels, while the catalyzer is cooled by flowing through the catalytically inactive channels. In conventional catalyzers, the catalyzer outlet temperatures are too low, however, to sufficiently stabilize the flames in the combustion chamber.
In view of the above disadvantages of the prior art, the invention is directed to a device that provides a compact construction and stability and homogeneity of the flames in the combustion chamber.
The invention is based on the general idea of creating a swirl flow from the fuel/oxidant mixture and increasing the temperature of the mixture prior to its entrance into the combustion chamber by use of a catalyzer. For this purpose, the device according to the invention comprises a flow-enabling catalyzer/swirl generator arrangement, in which part of the fuel/oxidant mixture is burned and which generates a swirl flow. The invention makes it possible to increase the stability and homogeneity of the flames in the combustion chamber and to reduce the pulsation risk. In addition, such a catalyzer/swirl generator arrangement may have a relatively short construction in the flow direction, so that the device overall has a compact construction.
In principle, it is possible to construct the catalyzer/swirl generator arrangement in such a way that it has a catalyzer and, immediately following the catalyzer in a downstream direction, a swirl generator. However, an embodiment in which the catalyzer/swirl generator arrangement comprises a catalyzer constructed as a swirl generator is preferred. In other words, the catalyzer or catalyzer body is constructed in such a way that the flow exiting from it has the desired swirl. With this construction, two functions, i.e., the catalytic combustion and the swirl generation, can be integrated into a compact component.
It is useful that the catalyzer/swirl generator arrangement comprises several flow channels extending essentially parallel, i.e., in the same direction, to each other, of which some, in particular approximately half, are constructed catalytically active, and the others catalytically inactive. The channels may be arranged distributed around a longitudinal center axis of the catalyzer/swirl generator arrangement, whereby this longitudinal center axis extends in the main flow direction of the catalyzer/swirl generator arrangement. According to an advantageous embodiment, the channels can be slanted in relation to the longitudinal center axis in such a way that the longitudinal direction of the channels in each case extends slanted in relation to a straight line that extends parallel to the longitudinal center axis. This results in an arrangement for the channels that causes the desired swirl flow to exit on the outflow side of the catalyzer/swirl generator arrangement, i.e., at the outlet ends of the channels.
In order to reduce the pressure loss during the flow through the catalyzer/swirl generator arrangement, the slant of the channels in relation to the longitudinal center axis may increase in the flow direction, in particular steadily or in a stepped manner as well as continuously or progressively, whereby the slant of the channels may have the value zero at the inlet, i.e., the channels then extend parallel to the longitudinal center axis with their inlet.
According to a special further development, the catalyzer/swirl generator arrangement may comprise, radially to the longitudinal center axis, several layers of a corrugated or folded first web material whose corrugations or folds form the catalytically active or catalytically inactive channels. An intermediate layer of a flat or smooth second web material is arranged between two adjoining layers in a radial direction. This construction ensures that radially adjoining corrugations or folds are unable to project inside each other, so that the channels always have unchanging flow cross-sections.